The cover of the January 2009 issue of O magazine says it all: "How Did I Let This Happen Again?" A photo of Oprah Winfrey at her current weight of 200 lb. is juxtaposed with an image of her formerly slender self. Inside the magazine, Winfrey writes, "I felt completely defeated. I thought, I give up. I give up. Fat wins."

That moment of yielding fully to addiction is what Alan Marlatt, director of the Addictive Behaviors Research Center at the University of Washington, calls the abstinence-violation effect (AVE). "The abstinence-violation effect is a form of black-and-white thinking," says Marlatt. "You blame [your failure] on internal factors that you consider beyond your control." (See what makes you eat more food.)

Those factors  whether they are, as in Winfrey's case, a thyroid condition that causes weight gain, or a belief that addiction is a disease that robs you of free will  are what derail thousands of quitters and abstainers from their New Year's resolutions. You could also call it the "f___ it" effect, the idea that once you cheat, you've blown it, so you might as well binge. In traditional 12-step programs for addiction, that line of thinking is encapsulated in the slogan "A drink equals a drunk." But understanding and overcoming AVE, says Marlatt, is crucial to conquering a problem behavior or dependency in the long term. You have to know what to do when you fall off the wagon to learn how to stay on it. (See the top 10 food trends of 2008.)

While studying cigarette smokers who were trying to quit in the 1970s, Marlatt discovered that people who considered the act of smoking a single cigarette after their quit date to be a complete defeat and evidence of an innate and permanent lack of willpower were much more likely to let a momentary lapse become a full-blown relapse. That was the start of Marlatt's work on AVE. Since then, he has become one of the world's leading authorities on preventing relapse. (See photos of vintage cigarette ads.)

Most people who try to change problem behaviors  whether it's overeating, overspending or smoking cigarettes  will slip at least once. Whether that slip provokes a return to full-blown addiction depends in large part on how the person regards the misstep. "People with a strong abstinence-violation effect relapse much more quickly," says Marlatt. A single slip solidifies their sense that they are a failure and cannot quit, creating a self-fulfilling prophecy.

So what should you do instead? For starters, don't berate yourself for being weak. Instead, tell yourself, "I made a mistake. What can I do differently next time? How can I learn from this?" says Marlatt. "This happens to almost everybody. It's not just you."

One of the most common mistakes addicts make is focusing on whether they are strong enough to change rather than on specific methods of coping. "It's like trying to ride a bike," says Marlatt. "You make mistakes and learn, and you don't give up if you don't immediately find your balance." If the bicycle is missing a wheel or is otherwise broken, then it requires fixing  simply willing it to work is not going to help you ride.

Also, says Marlatt, "most people think that if they have urges or cravings, there's something wrong, that you're not supposed to have them." In fact, they are a normal part of habitual behavior. "Notice and accept them," he says, and be mindful of when and why they occur. Most relapses happen when people are stressed or experience negative emotions, or are exposed to people, places or circumstances that are associated with addictive behavior  old drinking buddies, for instance, or the morning cup of coffee that was always paired with a cigarette. These triggers can't always be avoided, so they need to be negotiated carefully.

Marlatt teaches a technique called "urge surfing" as a way to cope. "The urge is like a wave," he says. "It goes up and down. You don't try to get rid of it, but accept it and let it pass." People tend to think that urges will escalate infinitely if they don't yield to them  but in fact, like a wave, they rise to a peak and then fall. That is, even if you don't give in, the urge dissipates.

Indeed, because of the way the brain is wired, each time an addict lets an urge pass without engaging in the unwanted behavior, it weakens the neural connections that underlie the desire; each time he or she rewards the craving with the bad habit, the brain pathways, and the addiction, are strengthened. It helps for people to remind themselves that if they can resist an addictive urge once, it will become easier and easier to do it again in the future.

Marlatt uses the acronym SOBER to instruct patients on how to deal with a slip or fight off the urge to do so. The S stands for stop: pause for a moment and consider what you are doing. O means observe: think about what you are sensing, feeling and experiencing, and what events led to the situation. B is for breathe: take a few deep breaths. Then, expand your awareness and remind yourself of what will happen if you keep repeating the unwanted behavior and how you will feel afterward. R stands for respond mindfully: remember that you have a choice, that you are not powerless, and that you don't have to continue the undesired behavior.

"Otherwise, you are on autopilot," says Marlatt. "The urge is driving you. So take a breathing space."

Marlatt is currently conducting studies of the latest version of his behavior-modification techniques  which he collectively calls "mindfulness-based relapse prevention"  in comparison with typical addiction treatment. His research, on alcohol and other drug abuse, isn't completed yet, but he says, "We're getting very positive results."

In the meantime, by keeping AVE in mind, perhaps Oprah and the rest of us will have a better chance of sticking with our 2009 resolutions.